1. Field of the Invention
The present invention relates to a system for isolating, controlling, or reducing condensation in a patient circuit or in a patient interface in a gas flow delivery system.
2. Description of the Related Art
Gas flow delivery systems are used to deliver a flow of gas to an airway of a subject. Such systems are typically used in the medical field to deliver gas to a patient. Examples of gas flow delivery systems in the medical field include a ventilator or respirator, which replaces or supplements a patient's respiration, and a pressure support system, which provides a flow of gas to an airway of a patient at an elevated pressure to treat a medical disorder, such as obstructive sleep apnea (OSA). Pressure support systems include, but are not limited to continuous positive airway pressure (CPAP) devices, which delivers a constant positive pressure to the airway of a patient over multiple respiratory cycles, and variable pressure devices where the pressure of the flow of gas delivered to the patient is variable.
Variable pressure devices include auto-titrating devices that are capable of changing a base pressure or pressure profile delivered to the patent based on a monitored condition of the patient. Other variable pressure devices change the pressure of the flow of gas during a respiratory cycle. These devices include the following: a proportional assist ventilation (PAV®), a proportional positive airway pressure (PPAP®) device, a C-Flex™ device, a Bi-Flex™ device, and a BiPAP® device manufactured and distributed by Respironics, Inc. of Pittsburgh, Pa. The BiPAP device is a bi-level pressure support system in which the pressure provided to the patient varies with the patient's respiratory cycle so that a higher pressure is delivered during inspiration than during expiration.
A typical gas flow delivery system comprises a pressure/flow generating system that produces a flow of gas for delivery to a patient and a system for communicating the flow of gas to the patient. The latter system typically includes a flexible conduit having one end coupled to the pressure/flow generating device and a second end portion that couples to an airway of patient through a patient interface. The conduit, which is also referred to as a patient circuit, carries the flow of gas from the pressure generating device during operation of the system. The patient interface device, typically in the form of a nasal, oral, or nasal/oral mask, is coupled to the second end portion of the conduit to communicate the flow of gas from the patient circuit to the airway of the patient.
Heated humidifiers have been developed for use with gas delivery system devices to humidify the gas supplied to the patient. A typical humidifier comprises a heated water reservoir connected in series with the delivery conduit between the flow generator and the patient interface. As the humidified gas moves through the patient circuit from the humidifier to the patient interface, condensation or rainout may from in the patient circuit or in the patient interface device. Condensation will occur if the gas leaving the humidifier is at a saturation level higher than that required to attain saturation at the lower temperature of the patient interface.
Condensation may also build up on the inner surface of the patient circuit and/or the patient interface. The formation of condensation in the patient circuit is not limited to the use of heated humidifiers. Condensation may also form whenever the ambient temperature is colder than the gas temperature of the patient circuit. Condensation may even form in the patient circuit without any form of humidification present, such as in winter.
Condensation in the patient circuit and/or patient interface is undesirable for several reasons. First, liquid in the patient circuit may reach the patient, where it could drip on the patient's face. Moist areas are also more prone to formation of bacteria. Additionally, gas flowing through any accumulated condensation may generate an annoying gurgling sound. To remove the condensation it is necessary for the patient or caregiver to periodically disconnect the patient from the gas flow/pressure generator, for example by removing the mask from the face or disconnecting the patient circuit from the mask or gas flow/pressure generator so that the condensed water can be drained. This process is disruptive and may interfere with the patient's therapy.